Metallic tanks such as water heater tanks, include tank openings and threaded weld fittings supported at the tank openings. One type of threaded weld fitting is a threaded weld spud or a metal pipe nipple welded to the outside of the tank over a tank opening. Examples of threaded weld spuds are disclosed in U.S. Pat. No. 5,158,200 to Vago et al. and U.S. Pat. No. 5,431,296 to Lewis, which are incorporated by reference herein in their entirety.
The threaded weld spud typically includes internal threads for receiving a threaded portion of a cold water supply line, a hot water supply line, or a sacrificial anode, for example. Welding the threaded weld spud onto a wall of the water heater tank could potentially result in the expulsion of molten material onto the internal threads of the spud, consequently damaging the internal threads of the spud and complicating threaded engagement between the spud and its mating component (a water supply line, for example).
Undesirable expulsion of molten material onto the internal threads of the spud could potentially damage the welded spud, rendering it useless, necessitating costly and labor intensive rework or replacement of the threaded weld spud and/or the entire tank. For those reasons, improvements to threaded weld spuds and improved methods of welding threaded weld spuds to tank walls are continually sought by tank manufacturers in the interests of performance, manufacturability, cost and/or time.